1. Field of the Invention
This invention relates generally to underwater storage facilities and more particularly to mobile seafloor storage and supply systems.
2. Description of the Prior Art
Military requirements for POL (petroleum, oils, lubricants) have increased rapidly over the past decade as force mobility has increased.
In World War II, fifty percent of the logistics supply tonnage going to troops overseas consisted of POL products. Estimates indicate that during the Viet Nam conflict this figure jumped to seventy percent of the tonnage supplied, and was rising. This means that those military units charged with the logistics support supply of combat forces must center more attention on POL related systems to meet current demands. Factors such as the continual increase in tonnage required, strategic doctrines that emphasize force mobility, and the loss of foreign bases make it more difficult to meet POL requirements. New concepts must be considered to meet these requirements. The present invention is a new POL storage and supply system that places emphasis on operation from the seafloor and is compatible with anticipated military needs and modes of operation.
Supply of POL to troops at advanced bases is currently achieved by off-loading moored tankers via pipeline to the beach. The POL coming ashore from a tanker is stored in and distributed from advanced base POL facilities such as the Marine Corps amphibious assault fuel system or the Army Tactical Marine Terminal. This approach to POL supply has become unsatisfactory because of rising concern for system security, mobility and capacity that results from changing military operational concepts.
In addition, certain types of landing crafts and lighters that have POL transport capabilities have been utilized occasionally. However, the relatively low storage capacity and high vulnerability of these vessels make them less than ideal candidates for the POL transport and supply mission. Helicopters and air cushion vehicles have also been utilized. These vehicles have high speed capabilities but they use large quantities of fuel and have limited cargo capacities.
Recently two alternative POL supply concepts have evolved. One concept uses POL-filled barges and the other concept utilizes flexible bags. The barge concept utilizes ships to transport the barges to an operational site where they are off-loaded and moored offshore. As needs for the POL develop, the barges are beached and unloaded, or they remain offshore and are unloaded via hoses to the beach. The flexible bag concept uses conventional ships to haul stored collapsible bags to the operational site where they are off-loaded, filled by a tanker and emptied via hose to the beach. Both of these systems having increased mobility over static on-land storage systems and both require a mooring system and are quite vulnerable to enemy actions.
One of the most promising ways to achieve high storage capability and improved security plus system mobility is by utilizing submerged off-shore storage structures. In this way, off-shore storage of POL would be minimized while still utilizing well-developed on-land distribution systems. The result is a system placing POl products in a concealed environment with minimum fire hazard and vulnerability to enemy action. In recent years, several such systems have been developed. However, all such structures have exhibited large buoyant forces which have produced severe anchorage problems and high stresses in the container walls. In addition, only a small percentage of the total volume of the structure could be utilized to store POL and the installation methods which required excessive amounts of time.